1. Field of the Invention
The present invention relates to the biaxially oriented multilayered film featuring easy separation. More specifically, this invention relates to the biaxially oriented multilayered film which comprises the mutually incompatible polymer layer of the aromatic polyester and olefinic polymer and which provides single layered films with the minimum electric discharge marks caused when the single layer film is obtained by separation of the multilayered film or the minimum fault due to electrically charged foreign substances caused by electric charge during separation.
2. Description of Related Art
The barcode based systems are currently used in the extensive field for transportation and distribution, process control in the plant, etc. There has been a growing demand for thermal ink-transfer printing ribbon used in this system. In the field of magnetic recording, there is also an increasing need for QIC (4/1-inch data cartridge) tape.
The film used for these purposes is thin, and there are many troubles such as breakdown of the film in the production process; productivity is low. To improve productivity and production economy, Japanese Patent Laid-Open Nos. TOKKAISHO 51-30862(1976), TOKKAISHO 56-113427(1981), TOKKAISHO 57-176125(1982), TOKKAISHO 58-5226(1983), TOKKAISHO 60-178031(1985), TOKKAIHEI 2-36517(1990) and TOKKAIHEI 2-131994(1990) disclose the method wherein the mutually incompatible polymers are co-extruded to get the multilayered film by at least uniaxial orientation of the resulting non-oriented film, and two or more products are produced by separating the single layered film from said multilayered film.
The inventors of the present invention have found out that, when the single layered film is separated from the multilayered film according to the method, film is electrically charged and foreign substances attach to the film in the separation, slitting or winding process. If charged voltage is increased, it is discharged resulting in discharge marks on the film. These foreign substances and electric discharge marks will cause such problems as rejection of ink or magnetic coat in the painting process on the film, for example, decrease of the yield in the painting process due to pimples on the roll surface generated by the foreign substances, and increased dropout due to magnetic coating stains.
Said electric charge can be eliminated and neutralized by an electric charge eliminator bar installed at the separation point. However, this method allows charged potential to be reduced to some extent, but fails to remove the discharge marks.
Another way is to apply static eliminating agent to each layer composing the multilayered film, but the bleed type static eliminating agent is incapable of working effectively for the multilayered film; furthermore, it gives rise to another problem such as surface contamination due to bleeding out of the static eliminating agent.